How to create and animate the water reflection (Caustics) on an object?
As @gandalf3 mentioned, Cycles is not great at this, if you want to make your render physically accurate; My approach can give you photo realistic results, which are not, however, physically accurate.



Water Movement

You can use a Displace modifier, a Stucci procedural texture and an empty for Texture Coordinates in order to simulate the water movement. Do keep in mind that you'll need a lot of samples in order to get a usable image and a build with the Metropolis patch.

To do this, first add a subdivided plane (Shift + A>Mesh>Plane); then, go to the Modifiers tab in the Properties editor and add a Displace modifier and press the New button to add a new texture. After that, go to the Texture tab and select Stucci; you can later tweak this setting for better results.



Then add a Empty, go back to the Modifiers of the plane and select Object in the drop down list for Texture Coordinates; after that, set the object to be the empty you created earlier.



You can then animate the position and/or rotation of the empty, in order to "animate" the water movement.

Then you can simply add some glossyness to the plane point a lamp at it and render.

Caustics Simulation

A better way is to simulate Throw Patterns on a Spotlight.

Add a Spotlight (Shift + A>Lamp>Spotlight); then add another plane, in the location of the spotlight, and move it down. After that, parent the plane to the spotlight, by selecting the plane first and then the spotlight and pressing Ctrl + P>Offset (Keep Offset). Now, go to the node editor and add a material to the plane, wich looks like the following node tree:



In order to animate the caustics, you can use a Vector Mapping node.



Here, you can animate the X and Y values, for the location, in order to move the caustic pattern around.

Now you can point the spotlight at your objects and git it a test render. Make sure the strength of the spotlight is rather high - I used 2000 - otherwise, you'll not see the light on your object. Also, you can control the softness of the throw pattern by adjusting the distance of the plane to the spotlight or the Size field found in the Lamp tab, on the Properties editor, when the Lamp is selected:



This gives me this result: